The effect of dairy whey protein components and a free amino acid mixture simulating whey protein on subjective feelings of appetite and subsequent food intake in healthy normal-weight young adult women

Each female subject participated in four session days with a minimum of two days between test days. Each subject was provided with a subject-specific breakfast meal to consume at least 3 h before the test session appointment and only water is permitted thereafter. Upon arrival at the laboratory, a baseline questionnaire to assess feelings of appetite and nausea was completed. A test preload meal was served to be consumed within 15 min. Subjects completed some questionnaires to assess their feelings of appetite and nausea every 15 min for 90 min. A final questionnaire was collected at 120 min and subjects were then provided with a hot meal and water to consume until comfortably full within 15 min. The time involvement for each subject on each session day was at least 180 min and there are 4 sessions, therefore 720 min. The 4 four test preload meals consisted of an orange-flaboured marmalade spread to which was added either whey protein isolate, isolated alpha-lactalbumin, isolated beta-lactoglobulin or a mixture of free amino acids simulating the amino acid composition of whey protein. Each preload spread (250 g) was accompanied with a slice (45 g) of toasted low-protein bread and 100 ml of water. The whey protein isolate preload meal served as the control. The preload meals were isoenergetic (~1800 kJ) and contained a mixture of carbohydrate (52 g) and protein or amino acids (52 g amino acid equivalent). All the ingredients in the preload meals are food-grade materials. The lunchtime test meal served 120 min following consumption of the preload meals comprised of a mixed homogeneous single hot fried rice test meal and bottled water. The hot fried rice test meal made in a commercial kitchen included white rice, minced chicken meat, eggs, peas, carrots, corn, chicken stock, salt, sugar, and vegetable oil. The fried rice test meal contained 36.8 g available carbohydrate, 8.5 g protein, 5.8 g fat and 1.0 g total dietary fibre per 100 g with a calculated metabolisable content of 982.2 kJ per 100 g. The amount of fried rice meal and water was measured before and after consumption using an electronic scale.